It is well known in the art to employ with pop-up type irrigation sprinklers a pressure regulator in the pop-up riser of the sprinkler to control and keep constant the pressure at which water from the sprinkler nozzle is ejected into the atmosphere. The use of such pressure regulators is particularly useful with pop-up sprinklers, which will be used where the source pressure supplied to the sprinkler may vary over wide ranges, such as typically found in residential applications or where the sprinklers are to be used in hilly terrain. By using a pressure regulator, the sprinkler nozzle will produce a spray pattern which will be substantially constant over a wide range of supply pressures, thereby assuring that optimum sprinkler performance is achieved even though the source pressure to the sprinkler may vary over wide ranges.
One such pressure regulator, which has been suggested for use within the pop-up riser of pop-up sprinklers, includes a flow seat secured within a lower portion of the stem or riser, and a flow tube that is mounted within the riser for limited reciprocation above the flow seat. The flow tube is typically spring-biased and centered within the riser by O-ring type seals that are disposed about the upper and lower end portions of the tube and which engage the inside side wall of the riser to seal the space between the outside of the tube and the inside of the riser between the seals. The flow tube raises and lowers relative to the flow seat to regulate the water from the source passing through the flow tube to the sprinkler nozzle in response to the inlet water pressure. By controlling the pressure to the nozzle through movement of the flow tube relative to the seat, a substantially constant water pressure at the nozzle can be maintained. A pop-up sprinkler of this pressure regulating stem (PRS) design and one having a grit-protected pressure regulator are respectively disclosed and claimed in U.S. Pat. Nos. 4,479,611 and 4,913,352, assigned to Rain Bird Corporation, which disclosure is incorporated by reference herein.
PRS pop-up sprinklers usually require either under-the-head check valves or built-in check values installed within the sprinklers below the flow tube to trap water in lateral irrigation pipes. Examples of the latter type are Seal-A-Matic™ check valves sold by Rain Bird Corporation. The Seal-A-Matic™ check valves eliminate the need for under-the-head check valves and are installed on commercially available PRS pop-up sprinklers. These check valves not only effectively trap water in lateral pipes, but they reduce wear on the irrigation sprinkler components by minimizing water hammer during initial operation.
There is a need for a pop-up sprinkler, having the advantages of the commercially available PRS pop-up sprinklers discussed in the above paragraph, with fewer parts, fewer manufacturing steps, a reduction in length, and lower cost.